<template>
  <div class="s-canvas">
    <canvas
      id="s-canvas"
      :width="contentWidth"
      :height="contentHeight"
    ></canvas>
  </div>
</template>
<script>
export default {
  name: 'captchaCavas',
  props: {
    identifyCode: {
      type: String,
      default: '1234',
    },
    fontSizeMin: {
      type: Number,
      default: 16,
    },
    fontSizeMax: {
      type: Number,
      default: 40,
    },
    backgroundColorMin: {
      type: Number,
      default: 180,
    },
    backgroundColorMax: {
      type: Number,
      default: 240,
    },
    colorMin: {
      type: Number,
      default: 50,
    },
    colorMax: {
      type: Number,
      default: 160,
    },
    lineColorMin: {
      type: Number,
      default: 40,
    },
    lineColorMax: {
      type: Number,
      default: 180,
    },
    dotColorMin: {
      type: Number,
      default: 0,
    },
    dotColorMax: {
      type: Number,
      default: 255,
    },
    contentWidth: {
      type: Number,
      default: 112,
    },
    contentHeight: {
      type: Number,
      default: 38,
    },
  },
  methods: {
    // 生成一个随机数
    randomNum(min, max) {
      return Math.floor(Math.random() * (max - min) + min);
    },
    // 生成一个随机的颜色
    randomColor(min, max) {
      const r = this.randomNum(min, max);
      const g = this.randomNum(min, max);
      const b = this.randomNum(min, max);
      return `rgb(${r},${g},${b})`;
    },
    drawPic() {
      const canvas = document.getElementById('s-canvas');
      const ctx = canvas.getContext('2d');
      ctx.textBaseline = 'bottom';
      // 绘制背景
      ctx.fillStyle = this.randomColor(
        this.backgroundColorMin,
        this.backgroundColorMax,
      );
      ctx.fillRect(0, 0, this.contentWidth, this.contentHeight);
      // 绘制文字
      // eslint-disable-next-line no-plusplus
      for (let i = 0; i < this.identifyCode.length; i++) {
        this.drawText(ctx, this.identifyCode[i], i);
      }
      this.drawLine(ctx);
      this.drawDot(ctx);
    },
    drawText(ctx, txt, i) {
      ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax);
      ctx.font = `${this.randomNum(this.fontSizeMin, this.fontSizeMax)}px SimHei`;
      const x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1));
      const y = this.randomNum(this.fontSizeMax, this.contentHeight - 5);
      const deg = this.randomNum(-10, 10);
      // 修改坐标原点和旋转角度
      ctx.translate(x, y);
      ctx.rotate((deg * Math.PI) / 180);
      ctx.fillText(txt, 0, 0);
      // 恢复坐标原点和旋转角度
      ctx.rotate((-deg * Math.PI) / 180);
      ctx.translate(-x, -y);
    },
    drawLine(ctx) {
      // 绘制干扰线
      // eslint-disable-next-line no-plusplus
      for (let i = 0; i < 5; i++) {
        ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax);
        ctx.beginPath();
        ctx.moveTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight),
        );
        ctx.lineTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight),
        );
        ctx.stroke();
      }
    },
    drawDot(ctx) {
      // 绘制干扰点
      // eslint-disable-next-line no-plusplus
      for (let i = 0; i < 20; i++) {
        ctx.fillStyle = this.randomColor(0, 255);
        ctx.beginPath();
        ctx.arc(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight),
          1,
          0,
          2 * Math.PI,
        );
        ctx.fill();
      }
    },
  },
  watch: {
    identifyCode() {
      this.drawPic();
    },
  },
  mounted() {
    this.drawPic();
  },
};
</script>
